Before this patch, the barracks would finish at the exact same time as SCV #15, thus allowing the building of the Orbital Command Right away. There was never any question - 15 OC was the best way to go. And it made the OCD part of me happy because of how perfectly it lined up with the barracks timing.
Now, since the barracks has an additional 5 seconds of build time, the nagging question is - do you stop at 15 SCVs and build the orbital right when the barracks is finished, or do you make a 16th SCV and build an orbital once it is done? The first option is 15 OC, and the second is 16 OC.
With 15 OC, you get faster MULEs, but you have 5 seconds of idle CC time. With 16 OC, your MULEs come out a bit slower, but your CC has constant production. I've been wanting to actually test which is better for a long time, but haven't done so until now.
Every time I watch a Terran stream, one of the biggest things I look for in build orders is whether the Terran does a 15 OC or a 16 OC. There isn't any set standard - I've seen different players do different things. My guess when the patch was first released was that eventually all Terran players will settle on one or the other, so I delayed actually testing it. I always did the 16 OC variation simply because the OCD part of me can't stand the 5 seconds of idle build time on the CC. However, to this day, there is no set standard, which surprises me.
I finally decided to run some tests on which is better to settle my mind.
Here are the results:
The top graph is the total mineral value in the 16 OC build minus the total mineral value in the 15 OC build. The bottom graph is simply the total mineral value of both the 15 OC and 16 OC builds. (The total mineral value is the current number of minerals + the cost of each building + the cost of each SCV, including the one currently in production). The bottom graph shows that the difference is surprisingly tiny. The top graph reveals, however, that the 16 OC build fares slightly better in the long run even though the income from MULEs comes a bit later. With 16 OC, you also get faster full saturation.
So, even though the difference between 15 OC and 16 OC is quite small, 16 OC is the better option and it should become the Terran standard. (Note: there are some cases in which the slightly earlier influx of minerals from MULEs matters, such as an allin).
tl;dr 16 OC is slightly better than 15 OC in terms of longer term economy and it should become standard.
EDIT: I did not run many tests - only 3 per build, so the data is not definite as to the amount of minerals gained. But it is true that the 16 OC is, by some small margin, better than 15 OC in the long run. The earlier MULE from the 15 OC can be used for some sort of allin or a slightly faster 1rax expo. So, in the case of a 1rax expo, 15 OC is probably better. Either way, it'd still be nice to see some standardization.
EDIT 2: I decided to do some follow-up work that is more theoretical - just based on SCV build times and orbital build times and the such. (40 minerals/minute per SCV until 16 SCVS, after that the income is an average of experimental data since it no longer increases linearly, 9th SCV sent out to build and never brought back).
The second graph is based on the first graph. You can see the expected income differences in the first graph and how they translate to being very close total mineral counts in the second graph.
Here is the difference between the two graphs (positive means more minerals in 16 OC, negative means more minerals in 15 OC):
You can see that the first spike shows that the extra 16th SCV is making some more money, and then the mules kick in for the 15 OC but the 16 OC catches back up. The total theoretical difference/advantage is about 9 minerals in favor of 16 OC. Not a very large difference, but there you have it.